Generally, in a process for detecting a metal plate, it is only possible to judge whether a defect is present and to determine its position if it is present in most case. However, it is more important to obtain quantitative information (such as a size and a profile) of the defect of the metal plate, which can be used as an important basis for evaluating a health status of the metal plate and guiding the reparation and maintenance of the metal plate.
With increasingly strict requirements on the safety of the metal plate, there are needs to determine the profile shape of the defect, to image the defect with high precision, and to visualize a detection result of the defect.
In the related art, an ultrasonic guided wave has the following features: low attenuation, far propagation distance, 100% coverage of the thickness of the metal plate by a sound field, easy adjustment of a guided wave mode, etc. Moreover, detection with guided waves of omnidirectional electromagnetic acoustic transducers for an area surrounded by the transducer array from multiple angles can provide more abundant and accurate defect information for high-precision imaging of the defect.
However, a strong degree of scattering occurs when the guided wave encounters the defect, which will cause more artifacts in a defect image re-established by a guided wave imaging method in the related art, resulting in blind detection regions and seriously affecting location and imaging accuracy of the defects of the metal material. In addition, a transducer array in a specific geometric structure only has a best matching-degree and sensitivity to a defect having the specific scattering feature. However, an actual defect is very complex, and shape and scattering characteristics thereof are varied, therefore, a serious mismatch is present between the transducer array in the specific geometric structure and the actual complex defect with varied scattering characteristics, and the transducer array in the specific geometric structure cannot always maintain a high sensitivity to the actual complex defect, thereby resulting in a limited detection and imaging precision to the actual defect.
At present, the array structure for detection is relative fixed and regular, there are few studies on the relationship between the array structure and the defect imaging accuracy, and there is no research on the dynamic adjustment and performance optimization of the geometric topology structure of the transducer array.